Bio-deterioration of Southern Pine Stakes at Geographically Different Testing Sites
Jun Zhang, J Horton
Southern pine (SP) sapwood is commonly used in preparing the standardized stakes for performance testing as referenced in the American Wood Protection Association (AWPA) Book of Standards. For example, the standardized above ground test methods E16/E18 and the standardized ground contact test method E7 all use sapwood of SP as the preferred wood species for preservative performance test. In this paper, the decay performance of untreated SP in the above ground and ground contact conditions were examined when the stakes were exposed at geographically different testing sites across the United States, and their decay trend over time at different sites were compared and reported.
The results from the E16 test in Hilo, HI demonstrated that untreated SP stakes had a relatively slower deterioration initially, however, the stakes started to have a steep decline after 2 or 3-years exposure in the field. All the stakes had complete failure after approximately 5 – 6 years.
The results from the E18 test in Hilo, HI test site showed that decay attack was observed after one-year exposure, and then the average decay rating started to drop markedly with a zero rating after about 5 years. For the Saucier, MS test site, the E18 stake showed minimal decay attack following the first year exposure, and then decay started to take off over the next few years. The stakes failed completely after 5-years exposure. For the Gainesville, FL test site, E18 test stakes appeared to have very slight fungal attack for the first 2 years, then started to show steady decline over the next 5-6 years, and the stakes failed completely after approximately 8-years exposure. The Dorman Lake, MS test site demonstrated similar decay trend as Gainesville site.
The results from the E7 stakes installed in Gainesville, FL site started to show quick deterioration after installation, and had a steep decay curve over the 2-years period. Most of the stakes had complete failure after approximately 2-years exposure. In comparison, the E7 stakes installed in the two HI sites and Saucier, MS testing sites appeared to have a less steep decay curve with a complete failure after approximately 3-years exposure. The E7 stakes installed in Dorman, MS had complete bio-deterioration after 4-years in ground exposure.